KR940006262B1 - Deflection unit having a thin-walled yoke ring for cathode-ray tubes - Google Patents

Abstract

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Description

1 is a schematic diagram of a TV display tube with a deflection device.

2A and 2B are rear and longitudinal cross-sectional views, respectively, passing through the yoke ring for a 90 ° hybrid deflection unit.

3A and 3B are rear and longitudinal cross-sectional views, respectively, passing through the yoke ring for a 110 ° (width angle) deflection unit.

4A and 4B are rear and longitudinal cross-sectional views, respectively, through the yoke ring for the black and white graphical display deflection unit.

5 is a schematic diagram of an imaging tube having a target and external connection means.

* Explanation of symbols for main parts of the drawings

1: Display tube 2: Cylindrical neck part

3: trumpet-shaped part 4: display screen

5: electrode system 6: deflection coil system

7, 7 ', 8, 8': deflection coils 9, 10, 11 and 12: yoke ring

13: imaging tube 14: target

15 external connection means 16 deflection coil system

17: focusing coil 18: ferrite ring

19 mu-metal screening

Detailed description of the invention

The present invention relates to a deflection unit for a cathode-raytube comprising a first and a second deflection coil system and an annular core of sintered oxidized ferromagnetic material.

The cathode ray tube in which the deflection unit is used may be a display tube (for example, a data graphic display tube, a color display tube or a projection television display tube), an oscilloscope tube or a camera tube. Camera tube deflection units usually have a cylindrical core, while indicator tube deflection units generally have a cup or funnel-shaped annular core. For mechanical strength, an annular core of sintered oxidized ferromagnetic material for a display tube, hereinafter referred to as a yoke ring, generally has a greater wall thickness than is necessary for its actual function as a core material for deflection coils. For example, certain types of ferrite yoke rings for monochrome display tubes with a mass of approximately 360 g, 55 mm in height and approximately 55 mm and 85 mm in upper and lower diameters have a wall thickness of 6 mm, which is unnecessarily high in view of the above standards. Value. 6 mm is the wall thickness which a ferrite yoke ring normally has.

Such a deflection unit is fixed to the neck of the display tube by a clamping band, as a result of which the net portion of the display tube supports the total weight of the deflection unit, which is very high in weight, which is a disadvantage. The display tube neck is not split. The current state of ferrite yoke rings with high dimensions in wall thickness is based on the assumption that the mechanical tightness necessary for adjustment during manufacture and mounting in the deflection unit is determined by the thickness. This assumption is also due to the lack of attention to the factors that determine the mechanical robustness of ferrite yoke rings. Thus, there is an essential problem: how to obtain a yoke ring of sintered oxidized ferromagnetic material which reduces the wall thickness and maintains mechanical robustness. Reduced wall thickness is also important for camera deflection units. In practice, only yoke rings in the form of non-metallic sleeves or rolls have been used so far in such deflection units, because ferrite yoke rings occupy too much space for use. The present invention is to solve this problem. According to the present invention, a deflection unit of the type described at the beginning has a thin wall of annular core, and the oxygen content of the sintered oxidized ferromagnetic material of the annular core at or near the surface thereof is ferromagnetic in the annular core. The oxygen content of the material is about the same as the oxygen component of the ferromagnetic material in the annular core so that the annular core is substantially stress free.

The present invention is made in recognition of the fact that the mechanical stress introduced during the sintering process plays a decisive role, although mechanical robustness is in fact associated with the wall thickness. It is principally recognized in the present invention that the ferrite yoke ring undergoes a reduction treatment during sintering.

Partial oxygen pressure measurements as a function of ferrite material frequently used in ioquering show that equibrium pressure at temperatures above 1150 ° C has already exceeded the value of 0.021 MPa (air). This means that the ferrite material loses oxygen during the sintering process, which may occur frequently in air (or in an atmosphere with less oxygen), typically at temperatures significantly higher than 1150 ° C., which means that the loss of ambient temperature during cooling It is the loss that compensates for oxygen intake means from the atmosphere. This penetration of oxygen occurs through the surface of the sintered product (product) where the temperature is attenuated as a result of the diffusion process, which occurs more slowly as the temperature drops. As a result, a surface layer is formed which is richer in oxygen than the material located further inward. Measurements also show that such inhalation of oxygen is associated with changes in the length of expansion or contraction based on the ferrite phase used. As a result, it can be seen that the formation of the surface layer is under compressive or tensile stress with respect to the remaining material. This local stress often leads to fragmentation of the sintered product. In the absence of such stresses, an iok ring with a fairly high breaking strength is produced, resulting in a product with sufficiently high mechanical robustness, with a fairly thin wall thickness and a fairly low weight.

Within the gist of the present invention, the wall thickness can be realized on the basis of the outermost diameter and length of the ferrite yoke ring smaller than 6 mm, in particular 4 mm and smaller. The present invention can successfully produce ferrite yoke rings with wall thicknesses of 3 mm and even 2 mm.

By using a thin-walled yoke ring structure, the weight is greatly reduced, the material is saved in the first embodiment, and the unit cost can be reduced, and in the second embodiment, the selection of the yoke ring material is expanded. Higher (more expensive) quality is available. For example, it becomes possible to use materials with low (power) losses. In recent years, when using an electric circuit, it is important that the power loss is kept as low as possible. In addition to reducing the weight, it is also important to reduce the space that can be achieved by the thin wall of the yoke ring, especially in the case of the imaging yoke ring.

Another advantage of the thin-walled yoke ring is that it consists of two halves, which can be fixed to each other by means of an adhesive (especially an adhesive layer of up to 10 μm). Bonding by the adhesive layer is satisfactory because the wall of the yoke ring of the present invention is very thin and therefore the weight of the yoke ring half is relatively light. In particular, a good adhesion between the two halves is obtained using the contact adhesive as the adhesive to fix the two halves. In conventional thick walled yoke rings, springs were used to secure two halves.

Oxygen content control to form the basis of the present invention can be implemented in a variety of ways. So far it has been described that the oxygen content at or near the surface must be at least different from the oxygen content in the yoke ring. The material differences can be accommodated when measurements are made that the thickness of the layer on the surface having an oxygen content different from the internal oxygen content of the ioque ring is too thin to form a mechanical stress exceeding the breaking limit of the material. This situation can be reached, for example in the case of MnZn-ferrite of at least 4.75 gcm ^-3 density, by providing the iok ring at a sufficiently high density.

Some embodiments of the present invention relating to an annular core for use with a deflection unit will be described in more detail with reference to the accompanying drawings and the description that follows.

1 is a schematic longitudinal sectional view of a display tube 1 for black or color television. It consists of a cylindrical neck portion 2 and a portion 3 adjoining in a trumpet shape closed at the front surface (left side in FIG. 1) by the display screen 4. In the neck 2 is shown an electrode system 5, in which one electron beam (for monochrome display tubes) or three electron beams extending from one plane (for color televisions) can be generated. In the region where the neck portion 2 changes into the trumpet-shaped portion 3, a deflection coil system 6 is provided on the tube 1 which coaxially surrounds the tube 1 and the system is an electron beam in the horizontal direction. Pair of deflection coils 7 and 7 'of deflection coils (Saddle-type), second pair of deflection coils 8 and 8' for deflecting the electron beam in a vertical direction and a pair thereof It comprises a yoke ring 9 for supporting the coils 8 and 8 '. As shown in FIG. 1, the shapes of the deflection coils 7 and 7 'and the yoke ring 9 are suitable for the trumpet-shaped portion of the display tube 1. Horizontal deflection coils 7 and 7 'are located on either side of the horizontal deflection plane, which coincides with three extending planes in the case of color television tubes. Vertical deflection coils 8 and 8 'are located on either side of the horizontal deflection plane. The vertical deflection plane is perpendicular to the horizontal deflection plane, thereby coinciding with the plane of the drawing.

The yoke ring 9 is made of a sintered oxide ferromagnetic material and is suitable for deflection coil pairs 7 and 7 'having a small operating range by having a trumpet shape.

Figure 2a is a rear view through the yoke ring for the deflection unit according to the present invention, Figure 2b is a longitudinal sectional view. In the case of the invention, the figure relates to a yoke ring 10 consisting of two halves and having a maximum outer diameter of 86 mm (on the cup side) and a minimum diameter of 54 mm (on the neck side). The deflection unit used (90 °) is in hybrid form, ie a toroidal field coil is wound on each yoke ring half. After the coil is wound on each of the yoke ring halves, the halves are held together by a contact adhesive such as, for example, cyanoacrylate.

Figure 3a is a rear view through the yoke ring for the deflection unit according to the present invention, Figure 3b is a longitudinal cross-sectional view. In the case of the present invention, the figure relates to a yoke ring 11 formed in one piece, which has a maximum outer diameter of 113 mm and a minimum outer diameter of 57.5 mm. The wall thickness of the yoke ring is 4 mm. The 110 ° 7 color deflection unit used is a double-saddle type, ie both line and field deflection coil systems are all surrounded together by a yoke ring in saddle form.

Figure 4a is a rear view through the yoke ring for the deflection unit according to the present invention, Figure 4b is a longitudinal cross-sectional view. In the case of the present invention, the figure relates to a yoke ring formed in one piece, the yoke ring having an outer diameter of 54 mm at the end of its maximum width. The wall thickness of the yoke ring 12 is 3 mm. The thickness of the conventional yoke ring was 6 mm. Due to the relatively long cylindrical neck, the yoke ring is a very demanding product. The deflection unit in which the yoke ring 12 is used is a black and white data graphic display device.

The generation of mechanical stress during the sintering / cooling treatment of the yoke ring is prevented in several ways, two of which are practical.

1) For example, in air, with sintering, one method is to use a lower sintering temperature not greater than approximately 0.06 MPa as the difference between the applied oxygen pressure and the equilibrium pressure of ferrite is good, resulting in a reduction of the atmosphere in the furnace. The property is low enough. In this way, the ferrite material loses a small amount of oxygen, which tends to slightly oxygen intake during cooling. This method is well selected if the magnetic property attenuation of the material is also undesirable.

2) Another method is the realization of a relatively high density during the sintering process. As a result, oxygen penetration during the cooling treatment is prevented in a way that is limited to an extremely thin surface layer, the thickness of which is too small to form a mechanical stress exceeding the breaking limit of the material, ie approximately 14 MPa. This solution is well chosen when a certain amount of attenuation is desired for the magnetic properties of the yoke ring material.

The two embodiments are described below.

I) Magnesium zinc ferrite ioque rings are prepared by mixing magnesium oxide, zinc oxide and iron oxide as raw materials in a predetermined ratio and preheating at a temperature of approximately 1150 ° C. After the grinding step, a diffusion-drying step is performed to yield a compressible powder. After shaping treatment by dry compression treatment, sintering is carried out in a directly heated gas furnace with a maximum temperature of approximately 1260 ° C. and an oxygen content of between 8 and 21 in the furnace atmosphere. After the cooling treatment, the product is not subjected to mechanical stress and becomes sufficiently strong against mechanical grinding treatment. The main dimension of the yoke ring of the selected embodiment is about 44 mm in height, inner neck diameter is about 47 mm, inner cup diameter is about 87 mm, and wall thickness is 3 mm. The weight of the ring is approximately 120g, and the weight of a conventional ring comparable to that is approximately 250g.

B) Zinc oxide ferrite ioque rings are prepared by mixing the raw materials of manganese oxide, zinc oxide and iron oxide in a predetermined ratio and preheating them at a temperature of approximately 180 ° C. After the grinding step, a diffusion-drying process is performed to yield compressible particles. Molding treatment is performed by dry-compression treatment. Subsequent sintering treatment is carried out in a gas-fired furnace, which is in the same range as in the above embodiment but has a slightly lower oxygen content and is directly heated at approximately 1350 ° C. This results in a density not lower than 4.75 g / cm 3. After the cooling treatment, the yoke ring is not subjected to mechanical stress and thus becomes sufficiently strong even for the mechanical grinding treatment. The main dimensions of the ring of the selected embodiment are approximately 55 mm in height, approximately 45 mm in inner diameter neck portion, approximately 85 mm in inner diameter cup, and 2 mm wall thickness. The weight of the ring is approximately 120 g and the weight of the conventional ring is approximately 360 g. Examples of other materials suitable for the manufacture of thin-walled yoke rings are LiZn ferrites and NiZn ferrites.

The invention also relates to a deflection unit for an imaging tube. 5 schematically shows an imaging tube 13 including a target 14 and an external connecting means 15. A deflection unit including a deflection coil system 16 is provided around the imaging tube 13. A focusing coil 17 is also provided around the imaging tube 13. For use in high line TV cameras, for example cameras for high-definition TVs (2000 lines), the system described above offers many advantages.

Mu-metal screening cylinders or mu-metel rolls are conventionally provided around the coil system of the imager, on the one hand increasing the deflection meter, and on the other hand screening is an external interferometer. (Among them, they are formed against the earth's magnetic field. The deflection meter becomes an alternating field, and horizontal deflection meters, especially with high frequencies, interfere with conventional mu-metal screening due to the low resistance of mu-metal. This is associated with the interference eddy current, which is indicated by severe linearity errors and deflection of the deflection system, which is particularly undesirable in the case of special imaging tubes for satellite navigation (so-called dissector tubes). For use in satellites, the deflector should be as linear as possible with electric current. And when it comes to be a function of the same time. When the electrically conductive material of the cylinder is provided to the magnetic field, induced changes is different from the main current form up accordingly.

The vortex can be minimized by using a ferrite ring 18 for magnetic field amplification, as is required in the display tube deflection unit. Preferably mu-metal screening 19 may be provided around the ferrite ring 18.

Since it is useful to provide the ferrite ring 18 only in very limited space, providing a thin walled ferrite ring is an important subject of the present invention. If a ferrite ring with a wall thickness of 6 mm cannot be used, for example a ferrite ring with a wall thickness of 2 mm may often be used in practice.

Deflection Unit for Cathode Ray Tubes and Annular Cores for Use

Claims (11)

Cathode ray tube (1) comprising a deflection coil system of first and second deflection coils (7,7 ', 8'8') and coil yoke in the form of annular core (9) of sintered oxidized ferromagnetic material In the deflection unit 6, the wall thickness of the annular core 9 is 6 mm or less, and the oxygen content of the ferromagnetic material on or near the annular core 9 is the remainder of the annular core 9. A deflection unit for cathode ray tubes, characterized in that the annular core is almost unstressed because it is approximately equal to the oxygen content in the portion. 2. Deflection unit for cathode ray tubes according to claim 1, characterized in that the wall thickness of the annular core (9) is in the range of 2 to 4 mm. 3. Deflection unit for cathode ray tubes according to claim 2, characterized in that the annular core (9) consists of two halves and is bonded together by an adhesive. The deflection unit for cathode ray tubes according to claim 3, wherein the adhesive layer has a thickness of 10 m. Cathode ray tube (1) comprising a deflection coil system of first and second deflection coils (7,7 ', 8,8') and coil yoke in the form of annular core (9) of sintered oxidized ferromagnetic material In the deflection unit (6), the wall thickness of the annular core (9) is 6 mm or less, and the annular core (9) has one layer on its surface, and the oxygen content in this layer is equal to that of the annular core (9). Deflection unit for cathode ray tubes, characterized in that the thickness of the layer is substantially different from the oxygen content in the remainder of the shaped core (9) such that the annular core (9) is virtually unstressed. 6. A deflection unit for cathode ray tubes according to claim 5, characterized in that the lorry core (9) is made of Mn-Zn ferrite and has a density of at least 4.7 g / cm. The deflection unit for cathode ray tubes according to claim 5, wherein the wall thickness of the annular core is in the range of 2 to 4 mm. 8. Deflection unit for cathode ray tubes according to claim 7, characterized in that the annular core (9) consists of two halves and is bonded together by an adhesive. The deflection unit for a cathode ray tube according to claim 8, wherein the adhesive layer has a thickness of at most 10 mm. Annular core for use in a deflection unit (6) as claimed in any of claims 2-4. Annular core for use in a deflection unit (6) as claimed in any of claims 6-9.

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